Multi-piece dual-chamber leadless intra-cardiac medical device and method of implanting same

ABSTRACT

A leadless intra-cardiac medical device (LIMD) includes an electrode assembly configured to be anchored within a first wall portion of a first chamber of a heart. The electrode assembly includes an electrode main body having a first securing helix, an electrode wire segment extending from the body, and a first segment-terminating contact positioned on the electrode wire segment. The device further includes a housing assembly configured to be anchored within a second wall portion of a second chamber of the heart. The housing assembly includes a body having a second securing helix, a housing wire segment extending from the body, and a second segment-terminating contact positioned on the housing wire segment. The device also includes a connector block that electrically connects the electrode wire segment to the housing wire segment by retaining the first and second segment-terminating contacts.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.13/352,005, filed Jan. 17, 2012, which relates to and claims prioritybenefits from U.S. Provisional Application No. 61/553,825, filed Oct.31, 2011, entitled “Intra-Cardiac Dual Chamber System and Method ofImplanting Same,” which is hereby incorporated by reference in itsentirety. This application also relates to U.S. patent application Ser.Nos. 13/352,167, filed Jan. 17, 2012 (now U.S. Pat. No. 8,781,605); andSer. No. 13,352,136, filed Jan. 17, 2012 (now U.S. Pat. No. 8,634,912),which are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

Embodiments of the present invention generally relate to implantedmedical devices, and more particularly to multi-piece, dual-chamberleadless intra-cardiac medical devices and methods of implanting suchdevices entirely within a heart of a patient. As used herein, the term“leadless” generally refers to an absence of electrically-conductiveleads that traverse vessels outside of the intra-cardiac space, while“intra-cardiac” means generally, entirely within the heart andassociated vessels, such as the SVC, IVC, CS, pulmonary arteries and thelike.

BACKGROUND OF THE INVENTION

Current implantable medical devices for cardiac applications, such aspacemakers, include a “housing” or “can” and one or moreelectrically-conductive leads that connect to the can through anelectro-mechanical connection. The can is implanted outside of theheart, in the pectoral region of a patient and contains electronics(e.g., a power source, microprocessor, capacitors, etc.) that providepacemaker functionality. The leads traverse blood vessels between thecan and heart chambers in order to position one or more electrodescarried by the leads within the heart, thereby allowing the deviceelectronics to electrically excite or pace cardiac tissue and measure orsense myocardial electrical activity.

To sense atrial cardiac signals and to provide right atrial chamberstimulation therapy, the can is coupled to an implantable right atriallead including at least one atrial tip electrode that typically isimplanted in the patient's right atrial appendage. The right atrial leadmay also include an atrial ring electrode to allow bipolar stimulationor sensing in combination with the atrial tip electrode.

Before implantation of the can into a subcutaneous pocket of thepatient, however, an external pacing and measuring device known as apacing system analyzer (PSA) is used to ensure adequate lead placement,maintain basic cardiac functions, and evaluate pacing parameters for aninitial programming of the device. In other words, a PSA is a systemanalyzer that is used to test an implantable device, such as animplantable pacemaker.

To sense the left atrial and left ventricular cardiac signals and toprovide left-chamber stimulation therapy, the can is coupled to the“coronary sinus” lead designed for placement in the “coronary sinusregion” via the coronary sinus ostium in order to place a distalelectrode adjacent to the left ventricle and additional electrode(s)adjacent to the left atrium. As used herein, the phrase “coronary sinusregion” refers to the venous vasculature of the left ventricle,including any portion of the coronary sinus, great cardiac vein, leftmarginal vein, left posterior ventricular vein, middle cardiac vein,and/or small cardiac vein or any other cardiac vein accessible by thecoronary sinus.

Accordingly, the coronary sinus lead is designed to: receive atrialand/or ventricular cardiac signals; deliver left ventricular pacingtherapy using at least one left ventricular tip electrode for unipolarconfigurations or in combination with left ventricular ring electrodefor bipolar configurations; deliver left atrial pacing therapy using atleast one left atrial ring electrode as well as shocking therapy usingat least one left atrial coil electrode.

To sense right atrial and right ventricular cardiac signals and toprovide right-chamber stimulation therapy, the can is coupled to animplantable right ventricular lead including a right ventricular (RV)tip electrode, a right ventricular ring electrode, a right ventricularcoil electrode, a superior vena cava (SVC) coil electrode, and so on.Typically, the right ventricular lead is inserted transvenously into theheart so as to place the right ventricular tip electrode in the rightventricular apex such that the RV coil electrode is positioned in theright ventricle and the SVC coil electrode will be positioned in theright atrium and/or superior vena cava. Accordingly, the rightventricular lead is capable of receiving cardiac signals, and deliveringstimulation in the form of pacing and shock therapy to the rightventricle.

Although a portion of the leads are located within the heart, asubstantial portion of the leads, as well as the IMD itself are outsideof the patient's heart. Consequently, bacteria and the like may beintroduced into the patient's heart through the leads, as well as theIMD, thereby increasing the risk of infection within the heart.Additionally, because the IMD is outside of the heart, the patient maybe susceptible to Twiddler's syndrome, which is a condition caused bythe shape and weight of the IMD itself. Twiddler's syndrome is typicallycharacterized by a subconscious, inadvertent, or deliberate rotation ofthe IMD within the subcutaneous pocket formed in the patient. In oneexample, a lead may retract and begin to wrap around the IMD. Also, oneof the leads may dislodge from the endocardium and cause the IMD tomalfunction. Further, in another typical symptom of Twiddler's syndrome,the IMD may stimulate the diaphragm, vagus, or phrenic nerve, pectoralmuscles, or brachial plexus. Overall, Twiddler's syndrome may result insudden cardiac arrest due to conduction disturbances related to the IMD.

In addition to the foregoing complications, implanted leads mayexperience certain further complications, such as incidences of venousstenosis or thrombosis, device-related endocarditis, lead perforation ofthe tricuspid valve and concomitant tricuspid stenosis; and lacerationsof the right atrium, superior vena cava, and innominate vein orpulmonary embolization of electrode fragments during lead extraction.

To combat the foregoing limitations and complications, small sizeddevices configured for intra-cardiac implant have been proposed. Thesedevices, termed leadless pacemakers (LLPM) are typically characterizedby the following features: they are devoid of leads that pass out of theheart to another component, such as a pacemaker can outside of theheart; they include electrodes that are affixed directly to the can ofthe device; the entire device is attached to the heart; and the deviceis capable of pacing and sensing in the chamber of the heart where it isimplanted.

LLPM devices that have been proposed thus far offer limited functionalcapability. These LLPM devices are able to sense in one chamber anddeliver pacing pulses in that same chamber, and thus offer singlechamber functionality. For example, an LLPM device that is located inthe right atrium would be limited to offering AAI mode functionality. AnAAI mode LLPM can only sense in the right atrium, pace in the rightatrium and inhibit pacing function when an intrinsic event is detectedin the right atrium within a preset time limit. Similarly, an LLPMdevice that is located in the right ventricle would be limited tooffering VVI mode functionality. A VVI mode LLPM can only sense in theright ventricle, pace in the right ventricle and inhibit pacing functionwhen an intrinsic event is detected in the right ventricle within apreset time limit. To gain widespread acceptance by clinicians, it wouldbe highly desired for LLPM devices to have dual chamber pacing/sensingcapability (DDD mode) along with other features, such as rate adaptivepacing.

It has been proposed to implant sets of multiple LLPM devices within asingle patient, such as one or more LLPM devices located in the rightatrium and one or more LLPM devices located in the right ventricle. Theatrial LLPM devices and the ventricular LLPM devices wirelesslycommunicate with one another to convey pacing and sensing informationthere between to coordinate pacing and sensing operations between thevarious LLPM devices.

However, these sets of multiple LLPM devices experience variouslimitations. For example, each of the LLPM devices must expendsignificant power to maintain the wireless communications links. Thewireless communications links should be maintained continuously in orderto constantly convey pacing and sensing information between, forexample, atrial LLPM device(s) and ventricular LLPM device(s). Thispacing and sensing information is necessary to maintain continuoussynchronous operation, which in turn draws a large amount of batterypower.

Further, it is difficult to maintain a reliable wireless communicationslink between LLPM devices. The LLPM devices utilize low powertransceivers that are located in a constantly changing environmentwithin the associated heart chamber. The transmission characteristics ofthe environment surrounding the LLPM device change due in part to thecontinuous cyclical motion of the heart and change in blood volume.Hence, the potential exists that the communications link is broken orintermittent.

SUMMARY OF THE INVENTION

Certain embodiments provide leadless intra-cardiac medical device (LIMD)configured to be contained within a heart of a patient. The deviceincludes an electrode assembly configured to be anchored within a firstwall portion of a first chamber of a heart. The electrode assemblyincludes an electrode main body having a first securing helix, anelectrode wire segment extending from the body, and a firstsegment-terminating contact positioned on the electrode wire segment.The device further includes a housing assembly configured to be anchoredwithin a second wall portion of a second chamber of the heart. Thehousing assembly includes a body having a second securing helix, ahousing wire segment extending from the body, and a secondsegment-terminating contact positioned on the housing wire segment. Thedevice also includes a connector block that electrically connects theelectrode wire segment to the housing wire segment by retaining thefirst and second segment-terminating contacts.

The connector block may include recessed channels having openings. Thefirst and second segment-terminating contacts pass through the openingsinto the recessed channels. Each of the first and secondsegment-terminating contacts may include a connection stud that isretained within a contact-receiving member of the connector block. Eachof the connection studs may include an expanded head integrallyconnected to a clamping tail. The electrode, the firstsegment-terminating contact, the housing, the second segment-terminatingcontact, and the connector block may all be within the heart of thepatient.

Certain embodiments provide a method of implanting a leadlessintra-cardiac medical device (LIMD). The method includes introducing anelectrode into a first chamber of the heart, anchoring the electrodeinto a first wall portion of the first chamber, the electrode beingcoupled to a proximal end of an electrode wire segment having asegment-terminating contact at its distal end; introducing a housinginto a second chamber of the heart, anchoring the housing into a secondwall portion of the second chamber, the housing being coupled to aproximal end of an housing wire segment having a segment-terminatingcontact at its distal end; and interconnecting the segment-terminatingcontacts with a connector block in order to electrically connect theelectrode and the housing, the connector block remaining implantedinside the heart throughout operation of the device.

The connector block may include recessed channels having openings, andinterconnecting may include forcing the segment-terminating contactsthrough the openings into the recessed channels.

Anchoring the electrode may include urging the electrode into the firstwall portion with a pusher tool, rotating the pusher tool, wherein therotating causes the electrode to rotate, and screwing the electrode intothe first wall portion through the rotating until the electrode issecurely anchored into the first wall portion. The method may alsoinclude removing the pusher tool from the electrode after the electrodeis securely anchored into the first wall portion, the implantedelectrode wire segment extending from the electrode to the pusher tool.

The method may also include joining a temporary electrode wire segmentand a temporary housing wire segment to the electrode and housing wiresegments, respectively, at the segment-terminating contacts; andconnecting the temporary electrode wire segment and the temporaryhousing wire segment to a pacing system analyzer (PSA) to test theelectrode and the housing. The method may also include disconnecting thetemporary electrode and housing wire segments from thesegment-terminating contacts within the first and second chambers of theheart.

Interconnecting may include pulling connection studs of thesegment-terminating contacts into contact-receiving members of theconnector block. The method may also include disconnecting the temporaryelectrode and housing wire segments from the segment-terminatingcontacts.

The anchoring the housing may include urging the housing into the secondwall portion with a pusher tool, rotating the pusher tool, wherein therotating causes the housing to rotate, and screwing the housing into thesecond wall portion through the rotating until the housing is securelyanchored into the second wall portion. The disconnecting may includeunscrewing the temporary electrode and housing wire segments from thesegment-terminating contacts.

The pusher tool may include a protruding portion that is received by areciprocal portion within the housing to ensure that rotation of thepusher tool causes a corresponding rotation in the housing. The pushertool may be slidably retained within a main lumen.

The electrode may be introduced into the heart before the housing.Alternatively, the housing may be introduced into the heart before theelectrode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified view of a human heart.

FIG. 2 illustrates a longitudinal axial view of a housing assemblyportion of a leadless intra-cardiac medical device (LIMD) within anintroducer assembly.

FIG. 3 illustrates a longitudinal axial view of an electrode assemblyportion of an LIMD within an introducer assembly.

FIG. 4 illustrates a simplified diagram of an LIMD connected to a pacingsystem analyzer during implanted.

FIG. 5A illustrates a sectional view of a connector block portion of anLIMD with elements of a housing assembly and electrode assembly passingthere through.

FIG. 5B illustrates a sectional view of detailed features of a connectorblock.

FIG. 6 illustrates a simplified view of an LIMD.

FIG. 7 illustrates a simplified view of an LIMD within a patient'sheart.

FIG. 8 illustrates an exemplary block diagram of the electricalcomponents of an LIMD.

FIG. 9 illustrates a flow chart of a process of implanting a LIMD.

DETAILED DESCRIPTION

FIG. 1 illustrates a simplified view of a human heart 50. The heart 50is generally enclosed in a double-walled sac called a pericardium, whichprotects the heart 50. The outer wall of the heart includes threelayers. The outer layer of the heart 50 is referred to as theepicardium, or visceral pericardium because it is also the inner layerof the pericardium. The middle layer of the heart 50 is referred to asthe myocardium and is composed of muscle that contracts. The inner layerof the heart 50 is referred to as the endocardium and is in contact withblood that is pumped through the heart 50.

As shown in FIG. 1, the heart has four chambers, a right atrium 52, aleft atrium 54, a right ventricle 56, and a left ventricle 58. Ingeneral, the atria 52, 54 are the receiving chambers, while theventricles 56, 58 are the discharging chambers. Deoxygenated bloodenters the heart 50 through the superior vena cava 60, for example, andpasses into the right atrium 52. The blood is then pumped through thetricuspid valve 62 into the right ventricle 56 before being pumped outthrough the pulmonary valve 64 into the pulmonary artery 66. The bloodis then oxygenated in the lungs and returns to the heart 50 through thepulmonary vein 68 into the left atrium 54, where it is then pumpedthrough the mitral valve 70 and into the left ventricle 58. Theoxygenated blood then travels from the left ventricle 58 through theaortic valve 72 and into the aorta 74, through which the oxygenatedblood is then circulated throughout the body.

FIG. 2 illustrates a longitudinal axial view of a housing introducerassembly 80, according to an embodiment. The introducer assembly 80includes a flexible, cylindrical, open-ended sheath 82 defining aninternal introducer passage 84 and having an open distal end 88. Thesheath 82 may be formed of various materials, including but not limitedto silicon rubber. The sheath 82 is configured to be maneuvered throughhuman vasculature, such as veins and arteries, and into the heart 50, byway of the superior vena cava 60 or the interior vena cava 85 (shown inFIG. 1).

A housing assembly 86 of a leadless intra-cardiac medical device (LIMD)is secured within the internal introducer passage 84 of the sheath 82near a distal end 88. The housing assembly 86 includes a body 89containing electronics that allow the LIMD to function as one of varioustypes of implantable devices, such as, for example, an implantablepacemaker, a cardiac resynchronization therapy (CRT) device, animplantable cardioverter-defibrillator (“ICD”), neurostimulator, or thelike. The LIMD may be configured for DDDR pacing (atrial and ventricularpacing, atrial and ventricular sensing, dual response and rate-adaptive,used for dual chamber pacemakers). A securing helix 90 extends from adistal end 92 of the housing assembly 86. The housing assembly 86 alsoincludes a conductive wire 94 covered with insulation that extends froma proximal end 96 of the body 89. The conductive wire includes one ormore electrical conductors that connect with electronics associated withthe body 89. The securing helix 90 may be a coiled helical wire having asharp distal end. All or a portion of the helix 90 may function as anelectrode. Additional electrodes, such as ring electrodes, may beincluded on the body 89.

A pusher tool 98 is also positioned within the sheath 82. The pushertool 98 is configured to slide through the sheath 82. The pusher tool 98has an internal passage 100 into which the wire 94 passes. As shown inFIG. 2, the pusher tool 98 is generally a longitudinal tube or the like.Similarly, the sheath 82 is also a longitudinal tube having the opendistal end 88. The pusher tool 98 is configured to be moved within thesheath 82. The pusher tool 98 is configured to slide, telescope, orotherwise move within the sheath 82.

A physician or surgeon operates the housing introducer assembly 80 at aproximal end (not shown). The proximal end may include controls thatallow the sheath 82 and the pusher tool 98 to be bent, curved, canted,rotated, twisted, or the like, so as to be navigated through a patient'svasculature. In an embodiment, a distal end of the pusher tool 98 may bebent, curved, canted, rotated, twisted, articulated, or the like throughoperation by the physician or surgeon manipulating the proximal end ofthe assembly 80. Movement of the distal end of the pusher tool 98 causesa corresponding movement in the sheath 82. Optionally, the distal end 88of the sheath 82 may be bent, curved, canted, rotated, twisted,articulated, or the like through manipulation of controls at theproximal end, which causes a corresponding movement in the pusher tool98. One or both of the sheath 82 and/or the pusher tool 98 areconfigured to be moved in such a manner.

The pusher tool 98 abuts into the proximal end 96 of the body 89. Asshown in FIG. 2, a pusher retention element 102, such as a notch,recess, divot, or the like is formed within the proximal end of the body89. A retaining element 104, such as a tab, spur, barb, extension, orthe like of the pusher tool 98 fits into the pusher retention element102. Therefore, rotation of the pusher tool 98 causes a correspondingrotation of the housing assembly 86. Optionally, the pusher tool 98 mayconnect to the body 89 through various other interfaces that ensuresynchronized rotation of the pusher tool 98 and the housing assembly 86.

In order to ensure that the pusher tool 98 remains securely abuttedagainst the proximal end 96 of the body 89 while within the internalintroducer passage 84 of the sheath 82, tension is applied to the wire94 in the direction of arrow A. As tension is applied to the wire 94 inthe direction of arrow A, the body 89 is forced in the same direction.Because the outer diameter of the body 89 exceeds the inner diameter ofthe pusher tool 98, the body 89 remains outside of the internal passage100 of the pusher tool 98. That is, the body 89 does not pass into thepusher tool 98. Instead, a base 87 of the body 89 abuts against thedistal end 106 of the pusher tool 98. As noted above, the retainingelement 104 of the pusher tool 98 engages the pusher retention element102 of the body 89, thereby ensuring that the body 89 does not rotaterelative to the pusher tool 98. Instead, rotation of the pusher tool 98and the housing assembly 86 is synchronized in that rotation of thepusher tool 98 causes a common rotation in the housing assembly 86.

FIG. 3 illustrates a longitudinal axial view of an electrode introducerassembly 110, according to an embodiment. The electrode introducerassembly 110 includes a flexible, cylindrical, open-ended sheath 112defining an internal passage 114 having an open distal end 118. Thesheath 112 may be formed of various materials, including but not limitedto silicon rubber. The sheath 112 is configured to be maneuvered throughhuman vasculature, such as veins and arteries, and into the heart 50, byway of the superior vena cava 60 or the interior vena cava 85 (shown inFIG. 1).

An electrode assembly 116 is secured within the internal passage 114 ofthe sheath 112 near a distal end 118 of the sheath 112. The electrodeassembly 116 may be place within an atrium of a patient's heart, whilethe housing assembly 86 shown in FIG. 2 is positioned within a ventricleof the patient's heart. The electrode assembly 116 includes a body 115and a conductive wire 124 covered in insulation that extends from aproximal end 126 of the body 115. The conductive wire includes one ormore electrical conductors that connect with one or more electrodesassociated with the body 115. A securing helix 120 extends from a distalend 122 of the electrode assembly 116. The securing helix 120 may be acoiled helical wire having a sharp distal end. All or a portion of thehelix 120 may function as an electrode. Additional electrodes, such asring electrodes, may be included on the body 115.

A pusher tool 128 is also positioned within the sheath 112. The pushertool 128 is configured to slide through the sheath 112. The pusher tool128 has an internal passage 130 into which the wire 124 passes. As shownin FIG. 3, the pusher tool 128 is generally a longitudinal tube or thelike. Similarly, the sheath 112 is also a longitudinal tube having theopen distal end 118. The pusher tool 128 is configured to be movedwithin the sheath 112. The pusher tool 128 is configured to slide,telescope, or otherwise move within the sheath 112.

A physician or surgeon operates the electrode introducer assembly 110 ata proximal end (not shown). The proximal end may include controls thatallow the sheath 112 and the pusher tool 128 to be bent, curved, canted,rotated, twisted, or the like, so as to be navigated through a patient'svasculature. In an embodiment, a distal end of the pusher tool 128 maybe bent, curved, canted, rotated, twisted, articulated, or the likethrough operation by the physician or surgeon manipulating the proximalend of the assembly 110. Movement of the distal end of the pusher tool128 causes a corresponding movement in the sheath 112. Optionally, thedistal end 118 of the sheath 112 may be bent, curved, canted, rotated,twisted, articulated, or the like through manipulation of controls atthe proximal end, which causes a corresponding movement in the pushertool 128. One of both of the sheath 112 and/or the pusher tool 128 areconfigured to be moved in such a manner.

The pusher tool 128 abuts into the proximal end 126 of the body 115. Asshown in FIG. 3, a pusher retention element 132, such as a notch,recess, divot, or the like is formed within the proximal end of the body115. A retaining element 134, such as a tab, spur, barb, extension, orthe like of the pusher tool 128 fits into the pusher retention element132. In this manner, rotation of the pusher tool 128 causes acorresponding rotation of the electrode assembly 116. Optionally, thepusher tool 128 may connect to the body 115 through various otherinterfaces that ensure synchronized rotation of the pusher tool 128 andthe electrode assembly 116.

In order to ensure that the pusher tool 128 remains securely abuttedagainst the proximal end 126 of the body 115 while within the internalintroducer passage 114 of the sheath 112, tension is applied to the wire124 in the direction of arrow B. As tension is applied to the wire 124in the direction of arrow B, the body 115 is forced in the samedirection. Because the outer diameter of the body 115 exceeds the innerdiameter of the pusher tool 128, the body 115 remains outside of theinternal passage 130 of the pusher tool 128. That is, the body 115 doesnot pass into the pusher tool 128. Instead, a base 117 of the body 115abuts against the distal end 136 of the pusher tool 128. As noted above,the retaining element 134 of the pusher tool 128 engages the pusherretention element 132 of the body 115, thereby ensuring that the body115 does not rotate relative to the pusher tool 128. Instead, rotationof the pusher tool 128 and the electrode assembly 116 is synchronized inthat rotation of the pusher tool 128 causes a common rotation in theelectrode assembly 116.

FIG. 4 illustrates a simplified diagram of the housing assembly 86 andthe electrode assembly 116 implanted within the heart 50, according toan embodiment. Referring to FIGS. 2-4, in order to implant the housingassembly 86 and the electrode assembly 116 into the heat 50, each of thehousing introducer assembly 80 and the electrode introducer assembly 110are introduced into a vein of a patient. Either the housing introducerassembly 80 or the electrode introducer assembly 110 may be introducedinto the vein first. During this time, a separate and distinct imagingsystem, such as a fluoroscopic imaging system, and/or a surgicalnavigation system may be used to assist in guiding the assemblies 80 and110 into the heart 50. For example, a surgeon may view a real-timefluoroscopic image of the patient's anatomy to see the introducerassemblies 80, 110 being maneuvered through patient anatomy.

The introducer assemblies 80, 110 are maneuvered through the vein andultimately into the inferior vena cava 85, for example, and into theright atrium 52. Optionally, the introducer assemblies 80, 110 may bemaneuvered from a vein that connects to the superior vena cava 60 andinto the right atrium 60. Again, as noted above, the introducerassemblies 80, 110 may be maneuvered into the heart at separate anddistinct times. For example, the housing introducer assembly 80 may bemaneuvered into the right atrium 52 before the electrode introducerassembly 110, or vice versa.

As shown in FIG. 4, the conductive wires 94 and 124 of the housingassembly 86 and the electrode assembly 116, respectively, areelectrically connected to a pacing system analyzer (PSA) 140, throughtemporary wire segments 95, 125. The PSA is used to ensure adequate leadplacement, maintain basic cardiac functions, and evaluate pacingparameters for the housing assembly 86 and the electrode assembly 116.In general, the PSA 140 is used to test the housing assembly 86 and theelectrode assembly 116.

As mentioned above, the housing assembly wire 94 connects to a temporaryhousing assembly wire segment 95. Similarly, the electrode assembly wire124 connects to a temporary electrode assembly wire segment 125. Thetemporary housing assembly wire segment 95 remains connected to thehousing assembly wire 94 during installation and testing. Similarly, thetemporary electrode assembly wire segment 125 remains connected to theelectrode assembly wire 124 during installation and testing.

Referring again to FIGS. 1-4, the electrode assembly 116 is maneuveredinto the right atrium so that the helix 120 is adjacent a right atrialappendage 142. The pusher tool 128 urges the helix 120 into the rightatrial appendage 142. Once the helix 120 contacts the right atrialappendage 142, the pusher tool 128 is rotated by a physician at theproximal end of the assembly 110 in the direction of arc C (FIG. 3),which causes the pusher tool 128 to rotate, which, in turn, drivesrotation of the electrode assembly 116 (shown in FIG. 3). Accordingly,the helix 120 rotates in the direction of arc C, while at the same timebeing urged into tissue in the right atrial appendage 142. As such, theelectrode assembly 116 is screwed into the right atrial appendage 142.Once the electrode assembly 116 is firmly secured into tissue in theright atrial appendage 142, the pusher tool 128 is pulled away from theelectrode assembly 116 in the direction of arrow B (FIG. 3). Because theelectrode assembly 116 is now anchored into the right atrial appendage142, the electrode assembly 116 remains secured thereto, while thepusher tool 128 separates and recedes away from the electrode assembly116. Similarly, the sheath 112 is also pulled away in the direction ofarrow B, leaving only the electrode assembly 116 and the wire 124 in theright atrium.

As shown in FIG. 4, the electrode assembly wire 124 includes asegment-terminating contact 144 that connects the, temporary electrodeassembly wire segment 125 to the electrode assembly wire 124. Thesegment-terminating contact 144 connects the wires together proximatethe right atrial appendage 142. For example, the segment-terminatingcontact 144 may connect the wires at a distance from the right atrialappendage 142 that prevents the segment-terminating contact 144 frompassing into the tricuspid valve 62. The remainder of the temporaryelectrode assembly wire segment 125 is then laid in the inferior venacava 85, passing out through the vein, and to the PSA 140.

After, or before, the electrode assembly 116 is anchored into the rightatrial appendage 142, the housing assembly 86 is anchored into the rightventricular apex 146. Referring again to FIGS. 1-4, the housing assembly86 is maneuvered into the right atrium 52, down through the tricuspidvalve 62 and into the right ventricle 56 so that the helix 90 isadjacent the right ventricular apex 146. The pusher tool 98 urges thehelix 90 into tissue at the apex 146. Once the helix 90 contacts theapex 146, a physician rotates the proximal end of the pusher tool 98,which causes the pusher tool 98 to rotate in the direction of arc D(FIG. 2). Rotation of the pusher tool 98 drives rotation of the housingassembly 86. Accordingly, the helix 90 rotates in the direction of arcD, while at the same time being urged into the apex 146. As such, thehousing assembly 86 is screwed into the apex 146. Once the housingassembly 86 is firmly secured into the apex 146, the pusher tool 98 isseparated and pulled away from the housing assembly 86 in the directionof arrow A (shown in FIG. 2). Because the housing assembly 86 is nowanchored into the apex 146, the housing assembly 86 remains securedthereto, while the pusher tool 98 separates and recedes away from thehousing assembly 86. Similarly, the sheath 82 is also removed and pulledaway in the direction of arrow A (FIG. 2), leaving only the housingassembly 86 in the right ventricle.

As shown in FIG. 4, the housing assembly wire 94 includes asegment-terminating contact 148 that connects the temporary housingassembly wire segment 95 to the implanted housing assembly wire 94. Thesegment-terminating contact 148 connects the wires together proximatethe inferior vena cava 85. For example, the segment-terminating contact148 may be connect the wires within the heart at a distance from theinferior vena cava 85 that prevents the segment-terminating contact 148from passing into the tricuspid valve 62. The remainder of the housingassembly wire segment 95 is then laid in the inferior vena cava 85,passing out through the vein, and to the PSA 140.

Once the electrode assembly 116 and the housing assembly 86 are anchoredin position and tested by the PSA 140, the temporary wire segments 95,125 may be disconnected from the PSA 140. Once the temporary wiresegments 95, 125 are disconnected from the PSA 140, a splicing member orconnector block may be positioned onto proximal ends of the temporarywire segments 95, 125, respectively, and slid up the segments until theymeet the segment-terminating contacts 144, 148. The connector block maybe moved over the wire segments 95, 125 into the heart 50 by way of aseparate pusher tool, or simply a separate and distinct wire that allowsthe connector block to be maneuvered into the heart 50.

FIG. 5A illustrates a sectional view of a connector block 150 and thesegment-terminating contacts 144, 148, of the housing assembly wire 94and the electrode assembly wire 124. The connector block 150 or splicingmember includes a main body 152, which may be formed of a conductivematerial, such as Titanium or stainless steel, covered by an insulativebiocompatible material 153, such as silicon rubber, for example. Themain body 152 includes wire passages 154, 156 at a proximal end 158. Thewire passages 154, 156 slidably receive the temporary wire segments 95,125, respectively. The wire passages 154, 156 lead intocontact-receiving members within the body 152. The contact-receivingmembers represent flared chambers 163 that may include spring terminalsor snap bulbs 162, 164, respectively, having expanded heads that arelocated and oriented toward the proximal end 158 of the connector block150. The snap bulbs 162, 164 allow the wires 94, 124 to pass therein.The snap bulbs 162, 164, in turn, communicate directly with recessedchannels 166, 168, respectively, having a smaller diameter than the snapbulbs 162, 164, respectively. The recessed channels 166, 168 are locatedand oriented toward a distal end 222 of the connector block 150. Therecessed channels 166, 168 connect to wire openings 170, 172,respectively, that allow the temporary wire segments 95, 125 to passtherethrough. The openings 170, 172, wire passages 154, 156 and theopening 182 are formed as self-sealing septum to enclose the housing ofthe connector block 150 when items are within or removed from eachopening or passage.

A maneuvering wire 180 connects to the distal end 158 of the main body152 at a central threaded opening 182 that may be between the wirepassages 154, 156 respectively. The maneuvering wire 180 threadablyconnects to the opening 182. The maneuvering wire 180 allows a surgeonto push and maneuver the connector block 150 over the temporary wiresegments 95, 125 into the patient's heart. As the connector block 150 ispushed in the direction of arrow E, the wire segments 95, 125 slidethrough the main body 152.

Each segment-terminating contact 144, 148 includes a connection stud190, 192, respectively, within a protective sheath 194, 196 or sleeve,respectively. Each connection stud 190, 192 includes an expanded head198, 200 oriented toward the connector block 150, respectively,integrally connected to a smaller clamping tail 202, 204, respectively,oriented away from the connector block 150. The connection studs 190,192 may be formed of Titanium, stainless steel, or the like. The heads198, 200 include threaded channels 206, 208, respectively, that receiveand threadably retain distal ends of the wires 125, 95, respectively.The clamping tails 202, 204 are each permanently secured to theconductive wire segments 210, 212, respectively. As shown, the temporarywire segments 95, 125 connect to the assembly wires 94, 124,respectively. However, as explained below, the temporary wire segments95, 125 are configured to detach from the assembly wires 94, 124.

The protective sheaths 194, 196 or sleeves may be formed of softsilicone, rubber, or the like. The protective sheaths 194, 196 includetapered ends 214, 216, respectively, connected to expanded mid-sections218, 220, respectively. The segment-terminating contacts 144, 148 areretained within the mid-sections 218, 220, respectively.

Referring to FIGS. 4 and 5A, as the connector block 150 is slid over thetemporary wire segments 95, 125 toward the segment-terminating contacts144, 148, the segment-terminating contacts 144, 148 cinch toward eachother, as shown in FIG. 5A. The connector block 150 continues to bemoved toward the segment-terminating contacts 144, 148. As the connectorblock 150 abuts the segment-terminating contacts 144, 148, the sheaths194, 196, respectively, abut into the distal end 222 of the connectorblock 150. With continued urging of the connector block 150 in thedirection of arrow E (shown in FIG. 5A), the connection studs 190, 192slide out of the sheaths 194, 196, respectively, as the tension of thewires 94, 124 pulls the studs 190, 192 into the connector block 150. Thesheaths 194, 196 are not rigid enough to pass through the wire openings170, 172. However, the expanded heads 198, 200 move into the wireopenings 172, 170, respectively, and flex the recessed channels 168,166, respectively, open. The expanded heads 198, 200 are then snapablyretained within the snap bulbs 164, 162, respectively. Accordingly, theassembly wires 94, 124 are effectively electrically spliced togetherthrough conductive elements (not shown), e.g., wires or traces, withinthe connector block .

After the connection studs 190, 192 are retained within the connectionblock 150, the sheaths 194, 196, respectively, simply hang on theassembly wires 124, 94, respectively, and the distal end 222 of theconnection block 150. A portion of the sheaths 194, 196 may becompressed within the wires openings 172, 170, respectively, therebyensuring that the sheaths 194, 196 do not slide down the wires 210, 212,respectively. However, because the sheaths 194, 196 may be formed of anon-rigid material, such as silicone or rubber, the sheaths 194, 196 maynot be susceptible to sliding down the wires 210, 212, respectively.

After the connection studs 190, 192 are snapably secured within theconnection block 150, the temporary wire segments 95, 125 may bemanipulated to threadably disengage from the heads 200, 198,respectively. Then, the temporary wire segments 95, 125 may be removedfrom the connectors 148, 144, respectively. Similarly, the wire 180 maybe manipulated to threadably disengage from the connector block 150 andbe removed, leaving only a LIMD defined by the housing assembly 86 andthe electrode assembly 116 that are conductively connected and/orspliced together through the connector block 150.

Alternatively, the segment-terminating contacts 144, 148 may connect toa joining mechanism other than the connector block 150. For example, thesegment-terminating contacts 144, 148 may themselves be threaded membersthat connect to a threaded joint. Optionally, the segment-terminatingcontacts 144, 148 may be plug members that engage a connector memberhaving reciprocal openings. Also, alternatively, the segment-terminatingcontacts 144, 148 may be shaped and sized to securely connect to variousother reciprocal structures.

Optionally, the connector block 150 may be loaded into a catheter. InFIG. 5A a distal end 157 of a catheter 155 is illustrated. The catheter155 may resemble a conventional catheter or resemble other existingtools used in other types of implants that has a proximal end with usercontrols that are adjusted by a physician, and a distal end that isconfigured to be manipulated in three dimensions (relative to thelongitudinal axis of the introducer) in order to guide and navigate thedistal end 157 of the catheter 155 to a desired tissue of interest.

The catheter 155 includes an interior lumen 163 defined by interiorsurfaces 165 of the catheter 155. The catheter 155 differs from aconventional catheter in that the catheter 155 has an interior surface165 that is stepped at the distal end 157 to form a block retentionpocket 159 that opens onto the distal end 157. The block retentionpocket 159 includes an internal ledge 161 that is spaced a desired depth167 from the distal end 157. The depth 167 may vary based on how much ofthe connector block 150 is to be held in the pocket 159. Optionally, thedepth 167 may be great enough that the entire connector block 150 isrecessed into the catheter 155 beyond the distal end 157.

The pocket 157 and connector block 150 include a keying feature 169,171. For example, a bump or other raised projection 171 may be providedon the ledge 161, while a mating indent or notch 169 is provided in theproximal end 158 of the connector block 150. The projection 171 andnotch 169 engage one another to prevent internal rotation of theconnector block 150 within the catheter 155. For example, the physicianmay desire that the connector block 150 not rotate. The projection 171and notch 169 cooperate to prevent rotation of the connector block 150.Alternatively, when a physician operates a user control to causerotation of the distal end 157 of the catheter 155, the connector block150 similarly rotates, thereby affording the physician detailed controlover the rotational orientation of the connector block 150. As oneexample, when the physician causes the housing assembly 86 and/orelectrode assembly 116 to rotate to screw in an active fixation memberthereon, it may be desirable that the connector block 150 rotate by asimilar amount to prevent entanglement of the wire segments 212, 210.

Optionally, the maneuvering wire 180 may be removed when the catheter155 is used. Optionally, the catheter 155 may be omitted entirely andinstead the wire 180 is used as the primary means to manipulate andadjust the connector block 150.

While not illustrated, it is understood that the components illustratedin FIG. 5A may be loaded into the electrode introducer assembly 110 orthe housing introducer assembly 80, or into a separate introducerassembly (not shown). Optionally, the catheter 155 may be used in placeof an introducer assembly.

FIG. 5B illustrates an enlarged detail view of an alternative embodimentfor a contact receiving member 463 within a connector block. In FIG. 5B,a portion of a connector block 450 is illustrated. The connector block450 includes a distal end 422 with an opening 470 that communicates witha contact receiving member 463. The contact receiving member 463includes opposed interior walls 455 having spring arms 465 providedthereon. The spring arms 465 are biased inward to a normal relaxedposition (as shown in FIG. 5B). The spring arms 465 include roundedfacing surfaces 453 that project into the open path through the contactreceiving member 463. The spring arms 465 are deflectable in thedirection of arrows 467 outward and away from one another.

In FIG. 5B, an end of a wire segment 412 is illustrated. The wiresegment 412 may correspond to a housing assembly wire 94 or to anelectrode assembly wire 124. The wire segment 412 includes a segmentterminating contact 402 provided on the end thereof. The segmentterminating contact 402 includes a mating end 416 and an opposed rearretention ledge 418. The mating end 416 includes a cavity with a taperedwall 414. The mating end 416 is configured to engage and deflect thespring arms 465 outward in. the direction of arrows 467 as the segmentterminating contact 402 is pulled into the contact receiving member 463.The segment terminating contact 402 moves to a position within thecontact receiving member 463 at which the tips 464 of the spring arms465 snap behind and under the ledge 418 to hold the contact 402 withinthe chamber 463.

In FIG. 5B, a stylet 461 is also illustrated. The stylet 461 includes acollet 458 provided on the outer end of the stylet 461. The stylet 461also includes a central rod 460 that controls the collet 458. The collet458 may be a sleeve with a (normally) cylindrical inner surface and aconical outer surface. The collet 458 is inserted into the cavityprovided in the distal end 416 of the contact 402 and expanded againstthe matching tapered wall 414. The outer surface of the collet 458expands to a slightly larger diameter, squeezing the tapered wall 414 ofthe contact 402. The rod 460 is operated to screw the threads 456 thatcause the collet 458 to expand and contract.

Optionally, the collet 458 may be formed in a different manner, suchthat the collect enclosed the outer perimeter of the contact 402 andsqueezes the outer surface of the contact 402 to grip the contact 402.

It should be recognized that the spring arms 465 may be used withvarious configurations of the contacts including the contacts 144, 148illustrated in FIG. 5A. Similarly, the wire segment 412 and contact 402may be used without the tapered wall 414. Instead, the wire segment 412may include threaded channels and join to a wire similar to the channel208 and wire 95 in the embodiment of FIG. 5A.

FIG. 6 illustrates a simplified view of a leadless intra-cardiac medicaldevice (LIMD) 230, according to an embodiment. The device 230 includes ahousing assembly 86 comprising a body 89 and a housing assembly wire 94,an electrode assembly 124 comprising a body 116 and an electrodeassembly wire 124, and a connector block 150. The connector block 150electrically connects components of the housing assembly 86 withcomponents of the electrode assembly 116.

FIG. 7 illustrates a simplified view of the LIMD 230 within the heart50, according to an embodiment. As shown, the LIMD 230 is entirelywithin the heart 50. No portion of the device 230 is outside the heart50. The device 230 may be programmed through the PSA 140 shown in FIG.4. Alternatively, or additionally, the device 230 may be programmedthrough a telemetry unit.

FIG. 8 shows an exemplary LIMD 800 configured for dual-chamberfunctionality from a primary location within a single side of the heart.For example, the LIMD 800 may be implemented as a pacemaker, equippedwith both atrial and ventricular sensing and pacing circuitry.Alternatively, the LIMD 800 may be implemented with a reduced set offunctions and components. For instance, the LIMD 800 may be implementedwithout ventricular sensing and pacing. The LIMD 800 may also beimplemented with an increased set of functions. For example, if the LIMD800 includes a coil type electrode, the LIMD may be configured toinclude cardioversion and/or shocking therapy capability.

The LIMD 800 has a housing 801 to hold the electronic/computingcomponents. The housing 801 (which is often referred to as the “can”,“case”, “encasing”, or “case electrode”) may be programmably selected toact as the return electrode for certain stimulus modes. Electronicswithin the housing 801 further includes a plurality of terminals 802,804, 806, 808, 810 that interface with electrodes of the LIMD. Forexample, the terminals may include: a terminal 802 that connects with afirst electrode associated with the housing assembly (e.g. a helixelectrode) and located in a first chamber; a terminal 804 that connectswith a second electrode associated with the housing assembly (e.g., aring electrode) and also located in the first chamber; a terminal 806that connects with a third electrode associated with the electrodeassembly (e.g. a helix electrode) and located in a second chamber; aterminal 808 that connects with a fourth electrode associated with theelectrode assembly (e.g., a ring electrode); and an additional terminal,810 that connect with one or more additional electrodes, if available.The type and location of each electrode may vary. For example, theelectrodes may include various combinations of ring, tip, coil andshocking electrodes and the like.

The LIMD 800 includes a programmable microcontroller 820 that controlsvarious operations of the LIMD 800, including cardiac monitoring andstimulation therapy. Microcontroller 820 includes a microprocessor (orequivalent control circuitry), RAM and/or ROM memory, logic and timingcircuitry, state machine circuitry, and I/O circuitry.

LIMD 800 further includes a first chamber pulse generator 822 thatgenerates stimulation pulses for delivery by one or more electrodescoupled thereto. The pulse generator 822 is controlled by themicrocontroller 820 via control signal 824. The pulse generator 822 iscoupled to the select electrode(s) via an electrode configuration switch826, which includes multiple switches for connecting the desiredelectrodes to the appropriate I/O circuits, thereby facilitatingelectrode programmability. The switch 826 is controlled by a controlsignal 828 from the microcontroller 820.

In the example of FIG. 8, a single pulse generator 822 is illustrated.Optionally, the LIMD 800 may include multiple pulse generators, similarto pulse generator 822, where each pulse generator is coupled to one ormore electrodes and controlled by the microcontroller 820 to deliverselect stimulus pulse(s) to the corresponding one or more electrodes.

Microcontroller 820 is illustrated as including timing control circuitry832 to control the timing of the stimulation pulses (e.g., pacing rate,atrio-ventricular (AV) delay etc.). The timing control circuitry 832 mayalso be used for the timing of refractory periods, blanking intervals,noise detection windows, evoked response windows, alert intervals,marker channel timing, and so on. Microcontroller 820 also has anarrhythmia detector 834 for detecting arrhythmia conditions. Althoughnot shown, the microcontroller 820 may further include other dedicatedcircuitry and/or firmware/software components that assist in monitoringvarious conditions of the patient's heart and managing pacing therapies.

The LIMD 800 includes sensing circuitry 844 selectively coupled to oneor more electrodes through the switch 826. The sensing circuitry detectsthe presence of cardiac activity in the right chambers of the heart. Thesensing circuitry 844 may include dedicated sense amplifiers,multiplexed amplifiers, or shared amplifiers. It may further employ oneor more low power, precision amplifiers with programmable gain and/orautomatic gain control, bandpass filtering, and threshold detectioncircuit to selectively sense the cardiac signal of interest. Theautomatic gain control enables the unit 802 to sense low amplitudesignal characteristics of atrial fibrillation. Switch 826 determines thesensing polarity of the cardiac signal by selectively closing theappropriate switches. In this way, the clinician may program the sensingpolarity independent of the stimulation polarity.

The output of the sensing circuitry 844 is connected to themicrocontroller 820 which, in turn, triggers or inhibits the pulsegenerator 822 in response to the absence or presence of cardiacactivity. The sensing circuitry 844 receives a control signal 846 fromthe microcontroller 820 for purposes of controlling the gain, threshold,polarization charge removal circuitry (not shown), and the timing of anyblocking circuitry (not shown) coupled to the inputs of the sensingcircuitry.

In the example of FIG. 8, a single sensing circuit 844 is illustrated.Optionally, the LIMD 800 may include multiple sensing circuit, similarto sensing circuit 844, where each sensing circuit is coupled to one ormore electrodes and controlled by the microcontroller 820 to senseelectrical activity detected at the corresponding one or moreelectrodes. The sensing circuit 844 may operate in a unipolar sensingconfiguration or in a bipolar sensing configuration.

The LIMD 800 further includes an analog-to-digital (A/D) dataacquisition system (DAS) 850 coupled to one or more electrodes via theswitch 826 to sample cardiac signals across any pair of desiredelectrodes. The data acquisition system 850 is configured to acquireintracardiac electrogram signals, convert the raw analog data intodigital data, and store the digital data for later processing and/ortelemetric transmission to an external device 854 (e.g., a programmer,local transceiver, or a diagnostic system analyzer). The dataacquisition system 850 is controlled by a control signal 856 from themicrocontroller 820.

The microcontroller 820 is coupled to a memory 860 by a suitabledata/address bus 862. The programmable operating parameters used by themicrocontroller 820 are stored in memory 860 and used to customize theoperation of the LIMD 800 to suit the needs of a particular patient.Such operating parameters define, for example, pacing pulse amplitude,pulse duration, electrode polarity, rate, sensitivity, automaticfeatures, arrhythmia detection criteria, and the amplitude, waveshapeand vector of each shocking pulse to be delivered to the patient's heart808 within each respective tier of therapy.

The operating parameters of the LIMD 800 may be non-invasivelyprogrammed into the memory 860 through a telemetry circuit 864 intelemetric communication via communication link 866 with the externaldevice 854. The telemetry circuit 864 allows intracardiac electrogramsand status information relating to the operation of the LIMD 800 (ascontained in the microcontroller 820 or memory 860) to be sent to theexternal device 854 through the established communication link 866.

The IMD 802 can further include magnet detection circuitry (not shown),coupled to the microcontroller 820, to detect when a magnet is placedover the unit. A magnet may be used by a clinician to perform varioustest functions of the unit 802 and/or to signal the microcontroller 820that the external programmer 854 is in place to receive or transmit datato the microcontroller 820 through the telemetry circuits 864.

The LIMD 800 may be equipped with a communication modem(modulator/demodulator) 840 to enable wireless communication with aremote device, such as a second implanted LIMD in a master/slavearrangement, such as described in U.S. Pat. No. 7,630,767. In oneimplementation, the communication modem 840 uses high frequencymodulation. As one example, the modem 840 transmits signals between apair of LIMD electrodes, such as between the can 800 and anyone of theelectrodes connected to terminals 802-810. The signals are transmittedin a high frequency range of approximately 20-80 kHz, as such signalstravel through the body tissue in fluids without stimulating the heartor being felt by the patient. The communication modem 840 may beimplemented in hardware as part of the microcontroller 820, or assoftware/firmware instructions programmed into and executed by themicrocontroller 820. Alternatively, the modem 840 may reside separatelyfrom the microcontroller as a standalone component.

The LIMD 800 can further include one or more physiologic sensors 870.Such sensors are commonly referred to as “rate-responsive” sensorsbecause they are typically used to adjust pacing stimulation ratesaccording to the exercise state of the patient. However, thephysiological sensor 870 may further be used to detect changes incardiac output, changes in the physiological condition of the heart, ordiurnal changes in activity (e.g., detecting sleep and wake states).Signals generated by the physiological sensors 870 are passed to themicrocontroller 820 for analysis. The microcontroller 820 responds byadjusting the various pacing parameters (such as rate, AV Delay, V-VDelay, etc.) at which the atrial and ventricular pacing pulses areadministered. While shown as being included within the unit 802, thephysiologic sensor(s) 870 may be external to the unit 802, yet still beimplanted within or carried by the patient. Examples of physiologicsensors might include sensors that, for example, sense respiration rate,pH of blood, ventricular gradient, activity, position/posture,temperature, minute ventilation (MV), and so forth.

A battery 872 provides operating power to all of the components in theLIMD 800. The battery 872 is capable of operating at low current drainsfor long periods of time, and is capable of providing high-currentpulses (for capacitor charging) when the patient requires a shock pulse(e.g., in excess of 2 A, at voltages above 2 V, for periods of 10seconds or more). The battery 872 also desirably has a predictabledischarge characteristic so that elective replacement time can bedetected. As one example, the unit 802 employs lithium/silver vanadiumoxide batteries.

The LIMD 800 further includes an impedance measuring circuit 874, whichcan be used for many things, including: impedance surveillance duringthe acute and chronic phases for proper LIMD positioning ordislodgement; detecting operable electrodes and automatically switchingto an operable pair if dislodgement occurs; measuring respiration orminute ventilation; measuring thoracic impedance; detecting when thedevice has been implanted; measuring stroke volume; and detecting theopening of heart valves; and so forth. The impedance measuring circuit874 is coupled to the switch 826 so that any desired electrode may beused.

The microcontroller 820 further controls a shocking circuit 880 by wayof a control signal 882. The shocking circuit 880 generates shockingpulses of low (e.g., up to 0.5 joules), moderate (e.g., 0.5-10 joules),or high energy (e.g., 811 to 40 joules), as controlled by themicrocontroller 820. Such shocking pulses are applied to the patient'sheart 808 through shocking electrodes, if available on the LIMD. It isnoted that the shock therapy circuitry is optional and may not beimplemented in the LIMD, as the various LIMDs described above andfurther below will typically not be configured to deliver high voltageshock pulses. On the other hand, it should be recognized that an LIMDmay be used within a system that includes backup shock capabilities, andhence such shock therapy circuitry may be included in the LIMD.

FIG. 9 illustrates a flow chart of a process of implanting an LIMD,according to an embodiment. At 900, an electrode assembly 116 with atemporary electrode wire segment 125 attached thereto is maneuvered intoa right atrium of a heart. The electrode assembly 116 may be positionedas such using an electrode introducer assembly 110, as described above.The electrode assembly 116 is maneuvered into a patient's vein, throughthe inferior or superior vena cava, and into the heart to arrive at theright atrium of the heart.

At 902, the electrode assembly 116 is anchored into the right atrium.For example, the electrode assembly 116 may be anchored into the rightatrial appendage, as explained above. Once the electrode assembly 116 isanchored, the electrode introducer assembly 110 is withdrawn, leavingthe electrode assembly with a temporary electrode wire segment 125attached, implanted in the heart.

Next, at 904, a housing assembly 86 with a temporary housing assemblywire 95 is maneuvered into the right ventricle. The housing assembly 86may be positioned as such using a housing introducer assembly 80, asdescribed above. At 906, the housing assembly 86 is anchored into theright ventricular apex. Once the housing assembly 86 is anchored inplace, the housing introducer assembly 80 is withdrawn, leaving thehousing assembly with a temporary electrode wire segment 95 attached,implanted in the heart. Notably, the housing assembly may be maneuveredand anchored before (or even at the same time as) the electrodeassembly.

At 908, the terminal ends of the temporary electrode wire segment 125and temporary housing wire segment 95 are attached to a PSA and thefunctionality of the LIMD is tested. At completion of testing, thetemporary wire segments are disconnected from the PSA. At 910, aconnector block 150 is placed over the temporary wire segments 95, 125and the connector block is then maneuvered over the wires into the heartas described above with reference to FIG. 5A. The connector block 150 isadvanced to engage the segment-terminating contacts 144, 148 of thehousing assembly wire 94 and the electrode assembly wire 124 to therebyestablish electrical connection between the assemblies.

At 912, the temporary wire segments 95, 125 are disconnected from theassembly wires 94, 124 and removed, thereby leaving the LIMDfully-functioning within the heart.

Thus, embodiments provide a pacing device configured to be entirelywithin a heart of a patient, and a method of implanting the same.Embodiments provide a device and method for dual chamber pacing, such asDDDR pacing, without leads that connect a device that is external to theheart. Unlike a conventional IMD, embodiments provide a device that hasno components outside the heart, thereby providing: a low infectionrate, elimination of Twiddler's syndrome, greater patient comfort,little or no skin erosion, and elimination of other problems associatedwith conventional pacemaker implantation.

It is to be understood that the above description is intended to beillustrative, and not restrictive. For example, the above-describedembodiments (and/or aspects thereof) may be used in combination witheach other. In addition, many modifications may be made to adapt aparticular situation or material to the teachings of the inventionwithout departing from its scope. While the dimensions, types ofmaterials and coatings described herein are intended to define theparameters of the invention, they are by no means limiting and areexemplary embodiments. Many other embodiments will be apparent to thoseof skill in the art upon reviewing the above description. The scope ofthe invention should, therefore, be determined with reference to theappended claims, along with the full scope of equivalents to which suchclaims are entitled. In the appended claims, the terms “including” and“in which” are used as the plain-English equivalents of the respectiveterms “comprising” and “wherein.” Moreover, in the following claims, theterms “first,” “second,” and “third,” etc. are used merely as labels,and are not intended to impose numerical requirements on their objects.Further, the limitations of the following claims are not written inmeans-plus-function format and are not intended to be interpreted basedon 35 U.S.C. §112, sixth paragraph, unless and until such claimlimitations expressly use the phrase “means for” followed by a statementof function void of further structure.

What is claimed is:
 1. A method of implanting a leadless intra-cardiacmedical device (LIMD), said method comprising: introducing an electrodeinto a first chamber of the heart; anchoring the electrode into a firstwall portion of the first chamber, the electrode being coupled to aproximal end of an electrode wire segment, the electrode wire segmenthaving a segment-terminating contact at its distal end; introducing ahousing into a second chamber of the heart; anchoring the housing into asecond wall portion of the second chamber, the housing being coupled toa proximal end of an housing wire segment, the housing wire segmenthaving a segment-terminating contact at its distal end; andinterconnecting the segment-terminating contacts with a connector blockin order to electrically connect the electrode and the housing, theconnector block remaining implanted inside the heart throughoutoperation of the device.
 2. The method of claim 1, wherein the connectorblock includes recessed channels having openings, the interconnectingoperation including forcing the segment-terminating contacts through theopenings into the recessed channels.
 3. The method of claim 1, whereinanchoring the electrode comprises: urging the electrode into the firstwall portion with a pusher tool; rotating the pusher tool, wherein therotating causes the electrode to rotate; and screwing the electrode intothe first wall portion through the rotating until the electrode issecurely anchored into the first wall portion.
 4. The method of claim 3,further comprising removing the pusher tool from the electrode after theelectrode is securely anchored into the first wall portion, theelectrode wire segment extending from the electrode to the pusher tool.5. The method of claim 1, further comprising: joining a temporaryelectrode wire segment and a temporary housing wire segment to theelectrode and housing wire segments, respectively, at thesegment-terminating contacts; and connecting the temporary electrodewire segment and the housing wire segment to a pacing system analyzer(PSA) to test the electrode and the IMD.
 6. The method of claim 5,further comprising disconnecting the temporary electrode wire segmentand the temporary housing wire segment from the segment-terminatingcontacts within the first and second chambers of the heart.
 7. Themethod of claim 6, wherein the disconnecting comprises unscrewing thetemporary electrode wire segment and the temporary housing wire segmentfrom the segment-terminating contacts.
 8. The method of claim 1, whereinthe interconnecting comprises pulling connection studs of thesegment-terminating contacts into contact-receiving members of theconnector block, and further comprising disconnecting the temporaryelectrode wire segment and temporary housing wire segment from thesegment-terminating contacts.
 9. The method of claim 1, whereinanchoring the housing comprises: urging the housing into the second wallportion with a pusher tool; rotating the pusher tool, wherein therotating causes the housing to rotate; and screwing the housing into thesecond wall portion through the rotating until the housing is securelyanchored into the second wall portion.
 10. The method of claim 9,wherein the pusher tool includes a protruding portion that is receivedby a reciprocal portion within the housing to ensure that rotation ofthe pusher tool causes a corresponding rotation in the housing.
 11. Themethod of claim 9, wherein the pusher tool is slidably retained within amain lumen.
 12. The method of claim 1, wherein the electrode isintroduced into the heart before the housing.
 13. The method of claim 1,wherein the housing is introduced into the heart before the electrode.14. The method of claim 1, further comprising removing a maneuveringwire from the connector block after the segment-terminating contacts areconnected within the heart.